A series of experiments are proposed to explore organismic and environmental factors that influences the reinforcing and subjective effects of sedatives and tranquilizers in normal volunteers. The reinforcing effects are measured using single or cumulative dose preference procedure, in which each drug is compared to a placebo. Subjective drug effects are measured using self-report questionnaires. In the first two studies, the relationship between habitual alcohol consumption and the reinforcing effects of diazepam and pentobarbital will be explored using the two preference procedures. In the third study we will compare preference for diazepam, oxazepam and buspirone, using the preference procedure. The fourth study will investigate the effect of rate of drug administration on the quality and magnitude of subjective responses to diazepam and pentobarbital. Finally, the fifth study will compare the subjective and reinforcing effects of ethanol and diazepam when these drugs are administrated under social (group) or solitary (isolated) conditions. The experiments are designed to explore variables that affect the reinforcing effects of drugs, and the results may elucidate some of the determinants of drug abuse.